The curing of monomeric materials to produce polymeric thermoset resins is well known in the art. In general, the polymerizable monomers have at least one and customarily more than one reactive group which serves as an active site for a curing or crosslinking polymerization to produce the thermoset resins. However, the crosslinking of many if not most polymerizable monomers, for example the curing of epoxy resins, requires the use of a curing agent, catalytic or stoichiometric, to cause the curing or crosslinking to occur at an acceptable rate. Even in the presence of most curing agents the rate of crosslinking is slower than desired and the addition of an accelerator is required to obtain sufficiently rapid curing. Some monomers will cure at an acceptable rate in the absence of a curing agent, but only upon the addition of high intensity energy, e.g., ultraviolet (UV) light.
There are other monomers wherein the active site is such that no additional curing agent or high intensity energy is required and the monomers will cure upon the application of heat. Such monomers are termed "self-curing". One class of such self-curing monomers include within the molecular structure moieties of an arylcyclobutene, e.g., a benzocyclobutene. Without wishing to be bound by any particular theory, it appears likely that upon application of heat the cyclobutene ring undergoes ring-opening to produce active intermediates which crosslink by oligomerization and other reactions with adjacent molecules.
A series of patents to Kirchhoff, illustrated by U.S. Pat. No. 4,540,763, describes the production and curing of a large number of benzocyclobutene derivatives including ethers of di(hydroxyphenyl) compounds such as di(hydroxyphenyl)alkanes, also termed bisphenol alkanes, wherein an ether oxygen directly links a phenyl ring of the di(hydroxyphenyl) compound to the six-membered ring of the benzocyclobutene group. The monomers of Kirchhoff are characterized by this direct link of a functional group to the six-membered ring. The monomers are said to be self-curing. A copending patent application, Ser. No. 349,547, filed May 9, 1989, relates to certain ester derivatives of polymeric materials wherein a pendant carboxy function of the polymer is connected to a arylcyclobutene moiety through an alkylene group. Copending application Ser. No. 349,546, filed May 9, 1989, is directed to similar ether derivatives of di(hydroxyphenyl) compounds where the ether oxygen is connected to the arylcyclobutene group through an alkylene group. It would be of advantage to provide additional arylcyclobutenealkyl ethers which self-cure upon application of heat to produce thermoset resins having good properties.